As Iran continues its pursuit of a nuclear capability, outside observers have debated just how worried the world should be. Optimists argue that since nuclear war would be suicidal, no government would ever risk it, and they think the Islamic Republic would be no exception. Pessimists argue that Iran's radical and unstable regime might behave in unpredictable ways and cannot be trusted. Both camps seem to agree that rationality is the key to deterrence; they disagree over whether a nuclear Iran would be rational.

Unfortunately, things aren't that simple. The link between rationality and deterrence is less direct than people think, and what constitutes rational behavior for the leaders of a particular country can be hard to read. Deterrence, in short, is a more complex issue than generally assumed.

These points are brought home forcefully by a careful look at attempts to keep Saddam Hussein in check, something that the recent release of a massive amount of captured Iraqi records finally makes possible. As a result of the Iraq war, the United States gained possession of a priceless cache of documents, records of interviews, and even tape recordings of many meetings that shed invaluable light on Saddam's behavior -- material that is now accessible to researchers at the Conflict Records Research Center, in Washington, D.C. Taken together with previously available information, what these records show is a leader who was extremely hard, occasionally even impossible, to deter, but for reasons that have little to do with irrationality.

Containing Saddam was difficult, even though he acted according to a coherent set of self-interested preferences. This was because the Iraqi leader tended to ignore inconvenient facts and unpleasant information. He would repeatedly construct convoluted scenarios that allowed him to believe events would play out in the way that he wanted, even though others could see that such outcomes were highly unlikely. Rather than regard information about an opponent's intentions or